CODEWITHSUNDEEP
javascriptnode.jsarraybuffer
Sergei Martianov
Sergei Martianov

Reputation: 301

Free strings and buffers in JavaScript

I know that JS engine automatically delete from memory "unused" objects. So if we have some enormous object and want to free memory we have to do something like this:

largeObject = null

And if we haven't any other links to our object it will be removed by engine soon. It's clear. But what if we have enormous string. For example we have read it from file:

largeString = fs.readFileSync('bigdata.txt', 'utf8')

Can we tell engine that we will not use this string?

largeString = null

It's work only for objects, but string is a primitive type.

Also will it work with buffers:

let largeData = rs.readFileSync('bigdata')
/* Some code */
largeData = null

JS engine should understand that we will not use this buffer and free it. But Buffer is inherited from Int8Array and the last is just view for some ArrayBuffer. Which is accessable by largeData.buffer. Of course after largeData = null we lose access to this ArrayBuffer and so memory should be free in some time. Am I right in this purpose?

I know, that JS is not language about memory manipulations, but in my opinion very important to understand how engine frees memory to minimize risk of the memory lick.

Upvotes: 0

Views: 1030

Answers (1)

D. Pardal
D. Pardal

Reputation: 6597

But what if we have enormous string.

Strings are primitive values just like numbers. You can't have references to strings. However, strings can be deallocated when they are not reachable.

JS engine should understand that we will not use this buffer and free it. But Buffer is inherited from Int8Array and the last is just view for some ArrayBuffer. Which is accessable by largeData.buffer. Of course after largeData = null we lose access to this ArrayBuffer and so memory should be free in some time. Am I right in this purpose?

You are right. Because the only way to access the buffer is through largeData.buffer, if there are no references to largeData, the buffer can also be deallocated.

It's worth noting that the EcmaScript Specification doesn't specify when/how garbage collection happens. In fact, an engine that never collects garbage may be completely spec-compliant. In practice, however, most engines do that, to prevent memory leaks.

Upvotes: 1

Related Questions